1. The problem statement, all variables and given/known data A plastic plate with refraction index of 1.5 is placed in the interior of a micro-wave oven which operates with a frequency of 2.5 x 10^9 Hz. If the micro-waves are perpendicular to the surface of the plate, what is the minimum thickness of the plate so that the maximum reflection of micro-waves occurs? 2. Relevant equations 3. The attempt at a solution I honestly don't even understand the premises of the problem.. I feel like the maximum reflection of micro-waves will occur when some destructive interference is minimized. Right? But what are the interfering waves in this case? Are some waves reflecting out of the top surface of the plate and some go all the way through and reflect at the bottom surface? In that case, why is that happening?